A sample of iodine is easiest to ship as a powder because it is , making it easy to break into small pieces.

Helium is less
than the elements that make up the air we breathe, so a balloon filled with helium will float in air.

Plastic is a compound of nonmetallic elements, so its
properties make it a popular coating for electric wires to prevent the current from escaping.

a. 12.5 kg

step-by-step explanation:

f = ma

so

m = f/a = (2500 n)/(200 m/s²) = 12.5 kg

1 n = 1 kg·m/s²

0.02

step-by-step explanation:

time of 9 192 631 770 periods of the radiation corresponding to the transition between the 2 hyperfine levels of the ground state of the caesium 133 atom at 0 k (but other seconds are sometimes used in astronomy)

2 x 503

step-by-step explanation:

its 1006